Mask blanks production method and mask production method

ABSTRACT

To prevent foreign matters from adhering to a substrate, etc., thereby causing inconveniences during storing and transporting a mask blank, or during manufacturing the mask blank and a mask. Thin films  2  and  3  formed in a mask thin film forming step of a mask blank manufacturing steps are covered by a dust-free protective film  5  formed of water-soluble material, thereby preventing foreign matters from adhering to the surface of the mask blank itself and preventing the surface of the mask blank from being damaged in the subsequent step, and when the mask blank is used, the dust-free protective film is removed.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a mask blank,which is a mask material of a mask for pattern transfer, and amanufacturing method for a mask.

BACKGROUND ART

For example, a mask blank, which is a raw material of a mask (reticule)used for a photolithography method, has a structure in which variouskinds of thin films such as a light-shielding film, which is alsoreferred to as an opaque film, and a phase shift film optically relatingto a transfer exposure light are formed on a substrate surface, andfurther, a resist film is formed on an uppermost layer of each kind ofthe thin film, or an antireflection film and a conductive film areformed on or under the resist film, and further a protective film, etc.,for protecting the thin films is formed.

A specific example of this mask blank includes a mask blank havingresist, whose uppermost layer is a resist film. The mask blank havingresist is formed in such a manner that each kind of thin film is formedon the substrate surface, and thereafter, the resist film is coatedthereon by a method such as a spin-coating method, and further aprescribed heating and drying process (including a cooling process),etc., is applied.

Note that the thin film formed on the substrate surface includes thelight-shielding film, the phase shift film (in a case of phase shiftmask), a reflecting film and an absorbing film (in a case of X-raymask), or the antireflection film, etc. The above-described thin filmshave some sort of relation with the transfer exposure light in such away as to allow the transfer exposure light to pass or inhibit theexposure light from passing, and function to form a prescribed transferpattern image on a transfer target.

FIG. 2 is a sectional view of the conventional mask blank having resist.As shown in FIG. 2, the mask blank 10 having resist is formed bysequentially forming a light-shielding film 2 and an antireflection film3 on a substrate 1 such as a glass, etc., and coating thereon a resistfilm 4 by the spin-coating method, etc. However, in many cases,unnecessary build-up parts 4 a are generated in the peripheral edge ofthe substrate 1 (specifically, a part along four sides of the mainsurface of the substrate 1), and also an unnecessary side face resist 4b is formed on the side face of the substrate 1.

Meanwhile, generally, the mask blank 10 having resist is contained in astorage container during transporting and storing it. FIG. 3 is aperspective view of an inner box 20 of a storage container 50 forcontaining plural sheets of mask blanks 10 having resists, and FIG. 4 isa sectional view of the storage container 50.

The storage container 50 includes an outer box 30 and the inner box 20,with the inner box 20 contained and fixed in the outer box 30. The innerbox 20 is contained and fixed so that a plurality of grooves 21 areprovided on a pair of side wall parts of the container which is arectangular shape with an upper opening and facing each other, and twosides 10 a and 10 b of the mask blank 10 having resist are inserted intothe grooves 21.

However, as described above, the unnecessary build-up parts 4 a and theunnecessary side face resists 4 b are formed on two sides 10 a and 10 bof the mask blank 10 having resist. Therefore, when the mask blank 10having resist is contained and/or taken in/out of the inner box 20, theunnecessary build-up parts 4 a and the unnecessary side face resists 4 bare made to touch and rub the grooves 21, etc., of the inner box 20. Inaddition, a vibration or a shock may be occurred in some cases, causedby moving and transporting it with the mask blank 10 having resistretained by the grooves.

In another case, the unnecessary build-up parts 4 a and the unnecessaryside face resists 4 b may also touch and rub the grooves 21 of the innerbox 20 by the vibration and the shock. As a result, the unnecessarybuild-up parts 4 a and the unnecessary side face resists 4 b are easilypeeled off/fallen off from the substrate 1 to become dust/dirt, whichadheres to the mask blank itself or each kind of processing device. Thisfinally causes a defect of the mask (including reticule), which is aproduct made from the mask blank as a raw material, or causes thepossibility of a low yield of the mask.

In order to solve the above-described problems, as a technique to removethe unnecessary resist film formed on the peripheral edge of thesubstrate 1, a method for selectively removing the unnecessary resistfilm of the peripheral edge of the substrate after coating resist hasbeen generally used (For example, see patent document 1, patent document2, and patent document 3).

(Patent Document 1)

Japanese Patent publication No. 57-13863

(Patent Document 2)

Japanese Patent Laid Open No. 63-160332

(Patent Document 3)

Japanese Patent Laid Open No. 2001-259502

DISCLOSURE OF THE INVENTION

However, it has been found that even in the case of the mask blank whichselectively removes the unnecessary resist film on the peripheral edgeof the substrate by the above-described method, etc., the trouble aswill be explained below is involved. Specifically, as described above,the inner box 20 is contained in the outer box 30 with an upper opening.The upper opening of the outer box 30 is freely opened and closed by alid 40. The lid 40 is provided with a substrate pressing member 41, andby the substrate pressing member 41, the head end face and the side endface of the mask blank 10 having resist are fixed.

Therefore, in addition to the part where the mask blank 10 having resistdirectly touches the inner box 20, etc., there are many parts where theinner box 20 and the outer box 30 touches to each other. Accordingly,possible factors are considered, contributing to extremely a lot offrictions such as friction in containing or taking the mask blank 10having resist in or out of the storage container 50, friction of acontact part between the mask blank 10 having resist and the inner box20, and friction of a contact part between the inner box 20 and theouter box 30, caused by vibration and shock during storing, moving andtransporting the mask blank. For this reason, it is extremely difficultto suppress dusting caused by the frictions of all the above-describedcontact parts. As a result, it has been found that it is extremelydifficult to effectively prevent foreign matters from adhering to thesurface (that is a resist film (uppermost layer)) of the mask blank orbuilding-up thereon, during moving, transporting, and storing the maskblank with the mask blank contained in a storage container.

Meanwhile, when manufacturing the mask by using the above-described maskblank having resist, the elapsed time and elapse number of days aftercoating resist until the exposure light step in a mask manufacturingstep are varied.

The variation of the time lapse and the number of days from post-coatingto the exposure light step affects the variation of a resistsensitivity, to become a CD variation. Therefore, the resist which canreduce post-coating drop of sensitivity and excellent in post-coatingstability in storing (excellent in post-coating PCD (Post Coating Delay)stability)) is selected and used as the resist formed on the mask blank.

For the resist excellent in post-coating stability, generally, anadditive (for example amine) called quencher is frequently addedintentionally. However, while the quencher makes the post-coatingstability good, there is a limitation on a design, or a limitation onselecting the resist for the mask blank, such that it is impossible toincrease the resist sensitivity to some extent or more. From theperspective of exposure productivity (mask productivity) or exposurequality (for example, variation in resist sensitivity when the resist isheated by electron beam exposure), the resist sensitivity is preferablyincreased.

Also, in circumstances where further pattern pitch narrowing isrequested, there have been raised problems such as deterioration inresist sensitivity or an amount of variation in resist sensitivitycaused by the time lapse and the number of days from the post-coating tothe exposure light step (that is, post-coating storage). Theconventionally allowed deterioration in resist sensitivity or the amountof the variation in resist sensitivity caused by the post-coatingstorage has not matched the required stability in resist sensitivity.Therefore, it is most preferable to form the resist film just before theexposure light step in the mask manufacturing steps. However, when themask blank formed with a thin film optically relating to a transferexposure light on the substrate surface, is contained in the storagecontainer and moved and transported to the mask manufacturing step orstored, adhesion of foreign matters or chemically polluted materials tothe surface of the mask blank (thin film optically relating to thetransfer exposure light) affects the quality of the resist to be coatedon the substrate. This finally causes a defect of the mask or causes thepossibility of a low yield of the mask.

In the above-described background, the present invention is provided. Afirst object of the present invention is to provide a method ofmanufacturing a mask blank and a method of manufacturing a mask capableof effectively preventing the possibility of inconveniency caused by theadhesion of foreign matters to a substrate, etc., during storing andtransporting the mask blank, or in a process of manufacturing a maskblank and a process of manufacturing a mask.

A second object of the present invention is to provide a method ofmanufacturing a mask allowing the mask blank to be supplied to a maskmanufacturing step while maintaining the original sensitivity of resist,suppressing lowering of resist sensitivity caused by storing the maskblank, and suppressing productivity reduction of a mask manufacture.

In order to solve the above-described problems, a first aspect of thepresent invention provides a method of manufacturing a mask blank, whichis a material of a pattern transfer mask formed with a thin filmoptically relating to a transfer exposure light and/or a thin film usedfor a mask manufacturing process on a substrate surface, comprising:

forming on a surface of the substrate the thin film optically relatingto the transfer exposure light and/or the thin film used for a maskmanufacturing process; and

forming a dust-free protective film covering the thin film formed in themask thin film forming step and/or the circumference of the thin filmthus formed,

-   -   wherein the dust-free protective film formed in the dust-free        protective film forming step covers the surface of the substrate        of the mask blank formed with the thin film and/or the        circumference to prevent the surface of the mask blank itself        from direct adhesion of foreign matters and from thereby being        damaged, and when the mask blank is used, the dust-free        protective film is removed.

A second aspect of the present invention provides the method ofmanufacturing the mask blank according to the first aspect, wherein thedust-free protective film is formed of a material removable by solventwhich does not affect the thin film formed on the surface of thesubstrate of the mask blank.

A third aspect of the present invention provides the method ofmanufacturing the mask blank according to either of the first or thesecond aspect of the present invention, wherein the solvent is water.

A fourth aspect of the present invention provides a method ofmanufacturing the mask blank according to any one of the first to thirdaspects of the present invention, wherein the thin film and/or thedust-free protective film formed on the peripheral edge of the substrateand used in the mask manufacturing process is removed by the solvent.

A fifth aspect of the present invention provides a method ofmanufacturing a mask having a mask pattern forming step in which themask pattern for pattern transfer is formed on a substrate, wherein byusing the mask blank manufactured by the method of manufacturing themask blank according to any one of the first to fourth aspects of thepresent invention, the mask pattern forming step is executed after thedust-free protective film of the mask blank is removed.

A sixth aspect of the present invention provides the method ofmanufacturing the mask according to the fifth aspect of the presentinvention, wherein the thin film optically relating to the transferexposure is formed on the surface of the substrate, a resist film isformed on the thin film, and a dust-free protective film is formed onthe resist film.

A seventh aspect of the present invention provides a method ofmanufacturing a mask including a mask pattern forming step to form amask pattern for pattern transfer on a substrate, wherein by using themask blank which is manufactured in the mask blank manufacturing step ofany one of the first aspect to the third aspect of the present inventionand in which the dust-free protective film is formed on the surface ofthe thin film optically relating to the transfer exposure light formedon the surface of the substrate, and after the dust-free protective filmof the mask blank is removed, the resist film is formed on the surfaceof the thin film, and the mask pattern is formed by subjecting theresist film to a mask pattern exposure processing.

Here, the mask blank of this invention has a broadly-defined structureincluding:

forming a light-shielding film having a light-shielding function forshielding a transfer exposure light;

forming a phase shift film having a function to bring about change ofphase differences to the transfer exposure light;

forming a halftone phase shift film, which is a translucent film, havinga light shielding function and also a function to bring about the changeof phase differences to the transfer exposure light;

forming a reflective film having a function to reflect the transferexposure light;

forming an absorbing film having a function to suppress the reflectionby absorbing the transfer exposure light; and

forming laminates of the above films, including all functional filmsrequired for realizing the function of the transmission type and thereflection type masks or the laminates of such films; or

forming resist-coated films by coating resist thereon, or furtherforming a single anti-reflection film and a single conductive film orthe laminates thereof on or under the resist film; and

forming an environmental resistance protective film on the resist filmor on the laminated films including the resist film. Or theabove-described films may not be formed.

Also, the mask blank includes a mask blank for LSI (Semiconductorintegrated circuit), and a mask blank for various kinds of PD (Paneldisplay). The material of the substrate is not particularly limited.Synthetic quartz glass, alkalifree glass, borosilicate glass,alumino-silicate glass, and soda lime glass are generally used as atransparent substrate. In addition, ultralow expansion glass or ultralowceramic is used as the substrate material for reflection type mask.

The thin film formed on the surface of the substrate includes thelight-shielding film, the phase shift film (in the case of phase shiftmask), the reflective film and the absorbing film (in the case of X-raymask), or the antireflection film, etc. These films relate to thetransfer exposure light in some way such as allowing and inhibiting thepassing of the transfer exposure light, and thereby functioning to forma prescribed transfer pattern image on the transfer target. In addition,the thin film formed on the surface of the substrate also includes thethin film used for a mask manufacturing process, for example, the resistfilm.

The resist may be either a negative type or a positive type. Also, thekind of the resist is not particularly limited, but may be anything suchas light (ultraviolet radiation and far ultraviolet radiation, etc,)exposure lithography resist and an electron beam light exposurelithography resist, etc. The resist forming method is not particularlylimited either, and may be anything such as a spin-coating method, aCapillary coating method, and a Scan coating method, etc.

Also, in the present invention, the dust-free protective film may beanything, provided that it neither dissolves into nor mix with the thinfilm and the resist film optically relating to the transfer exposurelight such as water-soluble resin, an organic solvent-soluble resin, aninorganic material film, and a light-shielding film etc., and it doesnot cause damage to the thin film, the resist film, and other thinfilms, etc., optically relating to the transfer exposure light, byforming and peeling (removing) the dust-free protective film. Moreover,the dust-free protective film is removed just before using the maskblank, that is, prior to the resist exposure light step, which is afirst step of the mask manufacturing step. In addition, when thedust-free protective film is formed by coating resist just before theresist exposure step in the mask manufacturing steps, the dust-freeprotective film is removed prior to coating resist. Accordingly, thefunction of the dust-free protective film is maintained from just afteran uppermost layer such as resist is formed to just before the maskblank is removed from the storage container 50. In addition, thedust-free protective film which does not affect the function of the maskblank or the thin film and the resist film optically relating to thetransfer exposure light or which does not affect the mask manufacturingstep is previously selected.

In addition, in the mask blank having resist, it is preferable to removean unnecessary resist film on the peripheral edge of the substratebefore forming the dust-free protective film, to remove the dust-freeprotective film of the contact part on the peripheral edge of thesubstrate after forming the dust-free protective film, or to remove theunnecessary parts of both the resist film and the dust-free protectivefilm. By the dust-free protective film, the surface of the blank isprotected from direct adhesion of dust. However, the generation of thedust itself can be suppressed by previously removing the unnecessaryfilm from the peripheral edge of the substrate or the contact part,thereby preventing pollution caused by the dust, for example, in theforming step or the removing step of the dust-free protective film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a mask blank manufacturing step.

FIG. 2 is a sectional view of the conventional mask blank having resist.

FIG. 3 is a perspective view of an inner box 20 of a storage container50 in which plural sheets of mask blanks 10 having resists arecontained.

FIG. 4 is a sectional view of the storage container 50.

-   1 Substrate-   2 Light-shielding film-   3 Antireflection film-   4 Resist film-   5 Dust-free protective film

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is an explanatory view of a mask manufacturing method accordingto an example of the present invention. The mask manufacturing methodaccording to the example of the present invention will be explained withreference to FIG. 1 hereunder.

Example 1

First, a mask blank is manufactured. As shown in FIG. 1(A), alight-shielding film 2 of 45 nm thickness containing chrome as a maincomposition was formed by sputtering on a suitably polished syntheticquartz substrate 1 of 6 inch×6 inch length and 0.25 inch thickness.Subsequently, an antireflection film 3 of 25 nm thickness containingchrome oxide as a main composition was formed on the light-shieldingfilm 2 by sputtering.

Next, as shown in FIG. 1(B), a resist 4 (Chemically amplified positiveresist for electron beam light exposure FEP171: developed by FUJIFILMArch Co, Ltd.) was spin-coated on an antireflection film 3 so that thefilm thickness after heating and drying treatment becomes 300 nm.

Next, as shown in FIG. 1(C), an unnecessary resist formed on theperipheral edge of the substrate 1 was removed and a dust-freeprotective film 5 was formed on the resist film 4. In this case, inremoving the unnecessary resist, the known apparatus for removingunnecessary film (for example, an apparatus described in Japanese PatentLaid Open No. 2001-259502) was used and organic solvent was used assolvent, and the unnecessary resist film on the peripheral edge of thesubstrate was thereby dissolved and removed. In addition, after theunnecessary resist was dissolved and removed, a hot plate whosetemperature was set to be 150° C. (proximity gap=0.2 mm) was used forheating and drying treatment for 10 minutes after coating, and a maskblank having resist was thereby prepared. Thereafter, by using a laserscan foreign matter inspection apparatus (developed by HITACHI,GM-1000), the number of foreign matter defects on the main surface ofthe mask blank was measured. In the measurement, the number of foreignmatters (having the size of 0.25 μm or more) on the surface of aneffective region 142 mm angle (substrate center) of the mask blank wasmeasured.

In addition, the dust-free protective film 5 was formed in such a mannerthat a solution of a water soluble resin having high purity TPF(developed by TOKYO OHKA KOGYO CO., LTD.) was spin-coated so that thefilm thickness after being subjected to baking and drying treatmentbecomes 800 nm. Thereafter, the unnecessary film removing apparatus (forexample, apparatus described in Japanese Patent Laid Open No.2001-259502) was used, and the unnecessary part of the dust-freeprotective film 5 on the peripheral edge of the substrate 1 wasdissolved and removed by using pure water as solvent. Subsequently, byusing the hot plate whose temperature was set to be 100° C. (proximitygap: 0.2 mm), the baking and drying treatment was applied for fiveminutes after coating the dust-free protective film, and the mask blankhaving the dust-free protective film of the present invention wasthereby achieved.

Here, the mask blank having dust-free protective film obtained in thisstage was contained in the inner box 20 set in the outer box 30 of thestorage container 50 as shown in FIG. 4, and a lid 40 is applied thereonand fixed by a vinyl tape. Then, the storage container 50 thuscontaining the mask blank was put in a bag made of resin and thermallysealed, thereby inhibiting the invasion of the foreign matters fromoutside, and then was packed for transport in a packing box formed of acushioning material made of styrene foam and corrugated board, and avibration test process was executed, assuming that the mask blank wastransported. The vibration test was conducted by following the process(Process in three directions XYZ so that the acceleration becomes twice)in an environment of a common vehicle of “MIL STD-810D 514.3).

Next, after the above-described vibration test process, assuming thatthe mask blank was stored, the storage container having mask blank afterthe above-described vibration test was taken out from the packing fortransport, then put in the bag made of resin and let it stand in a cleanroom where humidity and temperature were controlled for 30 days in astate of thermally sealed. Next, as shown in FIG. 1D, a mask blank 10after the storage process (in this case, the dust-free protective filmwas formed on the resist film) was taken out from the storage container50. Then, the dust-free protective film 5 made of water soluble resinwas dissolved and removed.

Here, the number of foreign matters on the surface of the mask blank wasmeasured again by the laser scan foreign matter inspection apparatusagain, and increase (difference) in foreign matters before and after thevibration test process was obtained. As a result, the increasing numberof the foreign matters was 0.6, which was an extremely small number. Inthis case, a mean value of the increasing foreign matters of five sheetsof mask blanks contained in one storage container 50 was used as theincreasing number of the foreign matters. Note that as a comparison, theincrease (difference) in foreign matters before and after the vibrationtest process was obtained under the same condition but providing thedust-free protective film. As a result, the increasing number of theforeign matters was 68. Incidentally, in a case where the dust-freeprotective film was not provided and also the peripheral edge of theresist was not removed, the increasing number of the foreign mattersobtained in similar way was 234.

Thereafter, the resist film 4 is patternwise exposed, subjected to PEB(Post-Exposure Bake) processing, and subsequently developed, thusforming a resist pattern 4 a. Here, the dust-free protective film 5 wasdissolved and removed by processing the substrate for one minute byspraying pure water, while rotating it at a prescribed number 500 rpm ofrevolutions so as to be dissolved and removed, and subsequently wasdried by rotating it at a high speed of 2000 rpm for 30 seconds.

In addition, the resist film 4 was exposed, heated (PEB), and developedas described below. Specifically, the resist film 4 (the above-describedFEP 171) was exposed to light (at an acceleration voltage of 20 kV andat an exposure of 3.5 uC/cm²), and after exposure to light, heated(Post-Exposure Bake processing, at 150° C., for 10 minutes), developed(by a splaying method, in 2.38% TMAH development liquid, for 60seconds), and a resist pattern 4 a was thereby formed.

Here, the dimension of a space part of the resist pattern 4 a thusformed (line and space pattern of design value of 400 nm) was measuredby measuring length SEM, and the value of 415 nm was thereby obtained asa result. Meanwhile, as a comparative example 1, in the mask blankprepared without using the dust-free protective film, the resist filmwas patterned under the same condition as described above, and a lineand space pattern having the design value of 400 nm was therebyobtained, and the dimension of the space part of the line and spacepattern was 411 nm. Difference in dimension of the space parts of bothof the line and space patterns was lower than a range of error caused byno stability in a patterning process including measuring. Accordingly,it can be judged that by adopting the dust-free protective film, theresist film was not affected.

As described above, in the mask blank (mask blank prepared by removingthe peripheral edge) prepared by “a method of selectively removing theunnecessary resist film on the peripheral edge of the substrate afterresist coating”, which is a generally widely used technique, the resistfilm is free of peeling and falling off caused by the friction betweenthe mask blank and the storage container by vibration. Therefore, ifcompared with the mask blank which does not remove the unnecessaryresist film on the peripheral edge of the substrate, the increase inforeign matters is obviously suppressed before and after the vibrationtest process. However, even if removing the unnecessary resist film onthe peripheral edge of the substrate, the increase in foreign matters isnot reduced to zero before and after the vibration test process.

The reason for this is considered that by the vibration test process(acceleration evaluation, assuming that the mask blank is moved andtransported), dust/dirt is generated by the friction between the maskblank and the storage container 50, and the friction in a contact partof each constituent member of the storage container 50 (for example, thecontact part between the inner box 20 and the inner side of the outerbox 30), thereby polluting the main surface of the substrate. It isconsidered that the above-described dust/dirt is generated by thefriction between each constituent member of the storage container 50, orpeeling and falling off of each film formed on the mask blank before theresist film is formed, resulting in adhering to the surface of the maskblank (on the resist film). It is obvious that the above-describedpolluted foreign matters finally become the cause of the defects of themask (including reticule), or the cause of low yield of the mask.

Example 2 and Comparative Example 2

Next, a mask manufacturing method according to another example will beexplained with reference to FIG. 1.

First, the mask blank is manufactured. As shown in FIG. 1(A), alight-shielding film 2 of 45 nm thickness containing chrome as a maincomposition was formed by sputtering on a suitably polished syntheticquartz substrate 1 of 6 inch×6 inch length and 0.25 inch thickness.Subsequently, an antireflection film 3 of 25 nm thickness containingchrome oxide as a main composition was formed on the light-shieldingfilm 2 by sputtering. Whereby, the mask blank having light-shieldingfilm (having no resist film 4 formed thereon) was prepared.

Thereafter, the number of defects of foreign matters on the main surfaceof the mask blank was measured by a laser scan foreign matter inspectionapparatus (developed by HITACHI, GM-1000). In the measurement, thenumber of foreign matters (having the size of 0.25 μm or more) presenton the surface of an effective region 142 mm angle (substrate center) ofthe mask blank was measured.

Subsequently, the dust-free protective film 5 was formed as will bedescribed below. The solution of a water soluble resin having highpurity TPF (developed by TOKYO OHKA KOGYO CO., LTD.) was spin-coated sothat the film thickness becomes 800 nm after baking and dryingtreatment, for example. Thereafter, the unnecessary film removingapparatus (for example, apparatus described in Japanese Patent Laid OpenNo. 2001-259502) was used, and the unnecessary part on the peripheraledge of the substrate 1 of the dust-free protective film 5 was dissolvedand removed by using pure water as solvent. Subsequently, by using thehot plate whose temperature was set to be 100° C. (proximity gap: 0.2mm), the baking and drying treatment was applied for five minutes aftercoating the dust-free protective film, and the mask blank havingdust-free protective film of the present invention was thereby achieved.

Here, the mask blank having dust-free protective film obtained in thisstage was contained in the inner box 20 set in the outer box 30 of thestorage container 50 as shown in FIG. 4, and a lid 40 is applied thereonand fixed by a vinyl tape. Then, the storage container 50 thuscontaining the mask blank was put in a bag made of resin and thermallysealed, thereby inhibiting the invasion of the foreign matters fromoutside, and then was packed for transport in a packing box formed of acushioning material made of styrene foam and corrugated board, and thecompletely same vibration test process as the example 1 was conducted,assuming that the mask blank was transported.

Next, after the above-described vibration test process, assuming thatthe mask blank was stored, the container having mask blank after theabove-described vibration test was taken out from the packing fortransport, then put in the bag made of resin and let it stand in a cleanroom where humidity and temperature were controlled, for 30 days in astate of thermally sealed. Next, as shown in FIG. 1D, a mask blank 10after the storing process (in this case, the dust-free protective filmwas formed on the light-shielding film (the resist film was not formed))was taken out from the storage container 50. Then, the dust-freeprotective film 5 made of water soluble resin was dissolved and removed.

Here, the number of the foreign matters on the surface of the mask blankwas measured again by the laser scan foreign matter inspectionapparatus, and the increase (difference) in the foreign matters beforeand after the vibration test process and 30-days storage was obtained.As a result, the increasing number of the foreign matters was 0.4, whichwas extremely small number. In this case, the mean value of the numberof foreign matters of five sheets of mask blanks contained in onestorage container 50 was used as the increasing number of the foreignmatters. Thereafter, a resist film 4′ was formed by coating resist, andthe resist film 4′ was subjected to a pattern exposure, and afterexposure, the resist film 4′ is heated (PEB processing) and developed,and the resist pattern a′ was thereby formed. The dust-free protectivefilm 5 was dissolved and removed in such a manner that the substrate wassubjected to processing for one minute by spraying pure water, whilerotating it at a prescribed number 500 rpm of revolutions so as to bedissolved and removed, and subsequently was dried by rotating it at ahigh speed of 2000 rpm for 30 seconds.

Note that as a comparative example 2, the increase (difference) in theforeign matters before and after the vibration test process and 30-daystorage was obtained, under the same condition but providing thedust-free protective film. As a result, the increasing number of foreignmatters was 57.

In addition, as shown in FIG. 1(B), the resist is applied on theanti-reflection film 3 in such a manner that the resist 4 (Chemicallyamplified positive resist for electron beam light exposure FEP171:developed by FUJIFILM Arch Co, Ltd.) was spin-coated on theantireflection film 3 so that the film thickness after heating anddrying treatment becomes 300 nm, and thereafter, a hot plate whosetemperature was set to be 150° C. (proximity gap=0.2 mm) was used forheating and drying treatment for 10 minutes after coating.

Moreover, the resist film 4 is exposed to light, heated (PEB process),and developed in such a manner that the resist film 4 (theabove-described FEP 171) was exposed to light (at an accelerationvoltage of 20 kV and at an exposure of 3.5 μC/cm²), and after exposureto light, heated (Post-Exposure Bake (PEB) processing, at 150° C., for10 minutes), developed (by a splaying method, using 2.38% TMAHdevelopment liquid, for 60 seconds g), and the resist pattern 4 a wasthereby formed.

Here, the dimension of a space part of the resist pattern 4 a thusformed (line and space pattern of design value of 400 nm) was measuredby measuring length SEM, and the value of 401 nm was thereby obtained asa result. Meanwhile, as the comparative example 2, the resist wasapplied on the mask blank stored for 30 days without using the dust-freeprotective film (in this case, the dust-free protective film was formedon the light-shielding film (the resist film was not formed)) under thesame condition as described above, followed by patterning to obtain theline and space pattern having design dimension of 400 nm. Then, thedimension of the space part of the line and space pattern was measuredby the measuring length SEM, and the value of 398 nm was therebyobtained as a result. Difference in dimension of the space parts of bothof the line and space patterns was lower than the range of error causedby no stability in a patterning process including measuring.Accordingly, it can be judged that by adopting the dust-free protectivefilm, the resist film was not affected.

Moreover, as described in the example 1, compared with the case wherethe dust-free protective film was formed on the resist film, thedimension of the space part of the line and space pattern having thedesign dimension of 400 nm is smaller by 14 nm (415 nm versus 401 nm),and the resist sensitivity was maintained high. It is judged that theabove-described difference in dimension (14 nm) is caused by thedeterioration in resist sensitivity due to 30-day storage. Namely, inthe case of the example 2 where the resist was applied just before lightexposure, original resist sensitivity could be obtained. Meanwhile, inthe case of the example 1 where the resist film was formed andsubsequently patterned after 30-day storage was passed, the originalresist sensitivity was damaged (lowered).

As described above, as shown in the examples 1 and 2, in the mask blankhaving the dust-free protective film, it became possible to prevent thefriction caused by the mask blank and the storage container 50 whenputting and taking out the mask blank in and from the storage container50, the friction caused by the mask blank and the storage container 50caused by vibration and shock occurred when storing, moving andtransporting the mask blank contained in the storage container 50, andthe friction caused by the contact part between each constituent memberof the storage container 50, and direct adhesion of dust/dirt therebygenerated to the mask blank itself. When manufacturing the mask by usingthe mask blank having resist, by removing the dust-free protective filmprior to the light exposure step, which is a first step of the maskmanufacturing step, and when the resist is applied and formed justbefore the light exposure step, by removing the dust-free protectivefilm prior to resist coating, the dust/dirt adhered to the surface ofthe dust-free protective film after the dust-free protective film wasformed was removed, thereby preventing the increase in surface defectsof the mask blank (foreign matters), and providing the quality of themask blank just after completion of the mask blank to the maskmanufacturing step. In addition, by using a water soluble resin havinghigh purity and showing almost neutrality and which does not affect thethin film and the resist film optically relating to the transferexposure light, for the dust-free protective film, pattern forming wasachieved without deterioration in function of the resist caused byforming, peeling and removing the dust-free protective film.

Here, in the example 1, the water soluble resin of almost neutral whichneither damages nor affects the chemically amplified positive resistfilm by forming or removing the dust-free protective film withoutdissolving the resist film or mixing with the resist film, was used forthe dust-free protective film. However, the dust-free protective film isnot limited to the water-soluble resin such as an organicsolvent-soluble resin, an inorganic material film, etc., provided thatit neither damages nor affects the resist film by forming and pealing(removing) the dust-free protective film, or the dust-free protectivefilm is not limited to the water-soluble resin, provided that it doesnot affect the function of the resist film (sensitivity, a residual filmrate, and pattern forming, etc), even if it slightly damages the resistfilm. When the uppermost layer is made of the film other than the resistfilm, the dust-free protective film is not limited to the water-solubleresin, provided that the function is neither damaged nor affected.

In addition, in the examples 1 and 2, the thickness of the coating filmof the dust-free protective film was set to be 800 nm, but it is notlimited thereto. For example, in the mask blank having resist, the filmthickness is not concerned, provided that the dust-free protective filmhas a film thickness capable of preventing the dust/dirt from directlyadhering to the resist film (blank)(function as the dust-free protectivefilm can be secured and maintained).

In addition, in the example 1, the dust-free protective film was formedafter selectively removing the unnecessary resist film on the peripheraledge of the substrate. However, the unnecessary resist film on theperipheral edge of the substrate may not be removed. Further, in theexamples 1 and 2, after forming the dust-free protective film, theunnecessary dust-free protective film on the peripheral edge of thesubstrate was selectively removed. However, it may not be removed.

However, it is preferable to remove the unnecessary resist film on theperipheral edge of the substrate before forming the dust-free protectivefilm, remove the dust-free protective film on the peripheral edge of thesubstrate after forming the dust-free protective film, or remove theunnecessary parts of both the resist film and the dust-free protectivefilm. Moreover, although the surface of the resist (blank) is protectedfrom the direct adhesion of the dust/dirt by the dust-free protectivefilm, by previously removing the unnecessary resist film and thedust-free protective film from the peripheral edge of the substrate orthe contact part, the generation of the dust/dirt itself can besuppressed. For example, the pollution caused by the dust/dirt in theforming step or the removing step of the dust-free protective film canbe prevented.

In addition, in the example 1, the unnecessary parts of the resist filmand the dust-free protective film on the peripheral edge of thesubstrate were removed just after forming each film. However, after thedust-free protective film is formed, the unnecessary parts of bothlaminated films may be removed at once. This is applied not only to thecase where the dust-free protective film is formed on the mask blankformed with only the resist film, but also the case where theantireflection film, the conductive film, and the environmentalresistance protective film are laminated.

In addition, in the example 2, the water soluble resin was selected tobe the dust-free protective film. However, the dust-free protective filmmay be anything, provided that it neither damages nor affects the thinfilm optically relating to the transfer exposure light even by formingand peeling (removing) the dust-free protective film. A film formingmethod may be anything such as a coating method, a sputtering method,etc., and a peeling method may also be anything such as a dissolving andremoving method or a dry etching method, etc.

In addition, in the examples 1 and 2, in order to examine the effect ofthe dust-free protective film, after coating resist (example 1) andafter forming the thin film optically relating to the transfer exposurelight (example 2), the number of foreign matters on the surface of themask blank were subsequently measured by the laser scan foreign matterinspection apparatus, and thereafter the dust-free protective film wasformed. However, the dust-free protective film may be formed immediatelyafter coating resist. Thus, it becomes possible to prevent the directadhesion of the dust/dirt to the surface of the mask blank (that is,resist film) in the foreign matter inspection step after coating resist.

In addition, in the examples 1 and 2, after passing through thevibration test process assuming that the mask blank was transported, andafter removing the dust-free protective film, the number of foreignmatters on the surface of the mask blank was measured by the laser scanforeign matter inspection apparatus prior to the exposure process.However, such a measurement is not necessarily required.

As shown in the examples 1 and 2, by the method of manufacturing themask blank and the method of manufacturing the mask of the presentinvention, the pollution by foreign matters (increase in foreignmatters) on the surface of the mask blank (that is, the resist film (oruppermost layer)) caused by the generation of the dust due to thefriction between the mask blank and the storage container 50, or thefriction between each constituent member of the storage container 50caused by the vibration or the shock occurred when storing, moving, ortransporting the mask blank contained in the storage container 50, islargely decreased.

By the method of manufacturing the mask blank, and the method ofmanufacturing the mask of the present invention, it becomes possible tosupply the mask blank to a mask manufacturing step, while maintainingthe surface defect (foreign matter) quality of immediately after coatingresist (immediately after completing mask blank). Whereby, the pollutioncaused by foreign matters (increase in foreign matters) on the surfaceof the mask blank by putting and taking out the mask blank in and fromthe storage container 50 and due to the vibration or the shock bystoring, moving, or transporting the mask blank contained in the storagecontainer 50, is suppressed, thereby also suppressing mask defects and alow yield of a mask manufacture.

In addition, the dust-free protective film can be formed by thespin-coating method used for forming the resist film, and can bedissolved and removed by a spray developing rotation processing methodused for the developing processing of the resist film. Therefore, theexistent technique or device can be diverted, thereby requiring no newtechnique or equipment for forming and removing the film.

INDUSTRIAL APPLICABILITY

As described above in detail, according to the present invention, first,it becomes possible to effectively prevent foreign matters from adheringto the substrate, etc., thereby causing inconveniences during storingand transporting the mask blank, or during the manufacturing process ofthe mask blank and the mask. Second, it becomes possible to supply themask blank to the mask manufacturing step, while maintaining theoriginal sensitivity of the resist, thereby suppressing the decrease insensitivity of the resist caused by storing of the mask blank, andthereby also suppressing the decrease in productivity of the maskmanufacture.

1. A method of manufacturing a mask blank for manufacturing a maskblank, which is a material of a pattern transfer mask, and in wich athin film optically relating to a transfer exposure light and/or a thinfilm used for a mask manufacturing process is formed on a surface of asubstrate, comprising: forming the thin film optically relating to thetransfer exposure light and/or the thin film used for a maskmanufacturing process, on the surface of the substrate; and forming adust-free protective film covering the thin film formed in the mask thinfilm forming step and/or the circumference of the thin film thus formed,wherein the dust-free protective film formed in the dust-free protectivefilm forming step covers the surface of the mask blank formed with thethin film and/or the circumference of the thin film, thereby preventingthe surface of the mask blank itself from direct adhesion of foreignmatters and from thereby being damaged in the subsequent step, and whenthe mask blank is used, the dust-free protective film is removed.
 2. Themethod of manufacturing the mask blank according to claim 1, wherein thedust-free protective film is formed of a material removable by solventwhich does not affect the thin film formed on the surface of thesubstrate of the mask blank.
 3. The method of manufacturing the maskblank according to either of claim 1, wherein the solvent is water. 4.The method of manufacturing the mask blank according to claim 1, whereinthe thin film and/or the dust-free protective film formed on theperipheral edge of the substrate and used in the mask manufacturingprocess is removed by the solvent.
 5. A method of manufacturing a maskincluding a mask pattern forming step to form a mask pattern for patterntransfer on a substrate, wherein by using the mask blank manufactured bythe method of manufacturing the mask blank according to claim 1, andafter removing the dust-free protective film of the mask blank, the maskpattern forming step is executed.
 6. The method of manufacturing themask according to claim 5, wherein the thin film optically relating tothe transfer exposure is formed on the surface of the substrate, aresist film is formed on the thin film thus formed, and a dust-freeprotective film is formed on the resist film thus formed.
 7. A method ofmanufacturing a mask including a mask pattern forming step to form amask pattern for pattern transfer on a substrate, wherein by using themask blank which is manufactured in the mask blank manufacturing step ofclaim 1 and in which the dust-free protective film is formed on thesurface of the thin film optically relating to the transfer exposurelight formed on the surface of the substrate, and after the dust-freeprotective film of the mask blank is removed, the resist film is formedon the surface of the thin film, and the mask pattern is formed bysubjecting the resist film to a mask pattern exposure processing.
 8. Themethod of manufacturing the mask blank according to either of claim 2,wherein the solvent is water.
 9. The method of manufacturing the maskblank according to claim 2, wherein the thin film and/or the dust-freeprotective film formed on the peripheral edge of the substrate and usedin the mask manufacturing process is removed by the solvent.
 10. Themethod of manufacturing the mask blank according to claim 3, wherein thethin film and/or the dust-free protective film formed on the peripheraledge of the substrate and used in the mask manufacturing process isremoved by the solvent.
 11. A method of manufacturing a mask including amask pattern forming step to form a mask pattern for pattern transfer ona substrate, wherein by using the mask blank manufactured by the methodof manufacturing the mask blank according to claim 2, and after removingthe dust-free protective film of the mask blank, the mask patternforming step is executed.
 12. A method of manufacturing a mask includinga mask pattern forming step to form a mask pattern for pattern transferon a substrate, wherein by using the mask blank manufactured by themethod of manufacturing the mask blank according to claim 3, and afterremoving the dust-free protective film of the mask blank, the maskpattern forming step is executed.
 13. A method of manufacturing a maskincluding a mask pattern forming step to form a mask pattern for patterntransfer on a substrate, wherein by using the mask blank manufactured bythe method of manufacturing the mask blank according to claim 4, andafter removing the dust-free protective film of the mask blank, the maskpattern forming step is executed.
 14. A method of manufacturing a maskincluding a mask pattern forming step to form a mask pattern for patterntransfer on a substrate, wherein by using the mask blank which ismanufactured in the mask blank manufacturing step of claim 2 and inwhich the dust-free protective film is formed on the surface of the thinfilm optically relating to the transfer exposure light formed on thesurface of the substrate, and after the dust-free protective film of themask blank is removed, the resist film is formed on the surface of thethin film, and the mask pattern is formed by subjecting the resist filmto a mask pattern exposure processing.
 15. A method of manufacturing amask including a mask pattern forming step to form a mask pattern forpattern transfer on a substrate, wherein by using the mask blank whichis manufactured in the mask blank manufacturing step of claim 3 and inwhich the dust-free protective film is formed on the surface of the thinfilm optically relating to the transfer exposure light formed on thesurface of the substrate, and after the dust-free protective film of themask blank is removed, the resist film is formed on the surface of thethin film, and the mask pattern is formed by subjecting the resist filmto a mask pattern exposure processing.